Process and apparatus for utilizing energy of flow



June 22 1926'. 1,590,049

L. F. MOODY PROCESS AND APPARATUS FOR UTILIZING ENERGY OF FLOW FiledAugust 27 1921 2 Sheets-Sheet 1 June 22 9 W26. 1,59%49 L. F. MOODYPROCESS AND APPARATUS FOR UTILIZING ENERGY 0F FLOW Filed August 27, 1921v 2 Sheets-Sheet 2 gw uemtoz Patented June 22, 1926.

UNITED STATES LEWIS FERRY MOODY, 0]! PHILADELPHIA, PENNSYLVANIA.

PROCESS AND APPARATUS FOR UTILIZING ENERGY OF FLOW.

Application filed August 27, 1921. Serial No. 496,154.

During the flow of fluid through various kinds of hydraulic apparatus itis frequently desired either to accelerate or to retard the velocity offlow. The acceleration of velocity can be easily and eflicientlyaccomplished, but it has been recognized that the retardation ordeceleration of velocity has, according to the methods heretoforeemployed, involved an unavoidable loss of energy. The methods in commonuse for decelerating the velocity of flow have consisted merely incarrying the flow through an enclosing conduit, the cross-sectional areaof which, measured normally to the motion of the stream, increasesgradually in the direction of flow. Reliance is placed on this increasein area, and the diverging wallsof the conduit, to cause the velocitytodecrease. It will be shown below, however, that this method necessarilyaccomplishes the deceleration at the expense of a loss of a considerableportion of the kinetic energy of the flow; and it is the object of thisinvention to reduce these losses, and thereby to enable velocity to bedecelerate-d more efficiently.

The method of this application consists in directing the flow upward,and assisting the desired deceleration by the direct downward action ofgravity acting upon the flowing mass. Any particle of the stream ifmoving upward freely and not influenced by impact from the preceding orfollowing particles, nor by viscous or tangential forces from particleson either side, will have its kinetic energy reduced by transformatloninto potential energy of os1tion1ts velocity head being reduce by theexact amount that its elevation above any fixed datum increases. By soforming the enclosing conduit walls that all particles of the streamwill decrease in velocity by the definite amount called for by thisrelation, natural or gravity deceleration will be secured, instead ofthe forced or induced deceleration of the methods heretofore used.

Fig. 1 is a diagrammatic representation of a portionof a verticallydirected simple conduit illustratin the invention.

Fig. 2 is a similar view of a spreading conduit.

Fig. 3 is a vertical sectional elevation of a turbine draft tubeillustrating the invention, and

Figs. 4 to 8 are diagrammatic illustrations of modifications adaptingthe invention for use with pumps, turbines, etc.

Consider first a simple conduit in which the flow is substantiallyparallel to the axis, as in Fig. 1; and at any two sections a and I) letthe respective cross-sectional areas he A and A, the correspondingvelocities v, and '0, and the elevations of the two sections 2, and 2.For a substantially incompressible fluid such as water the quantityflowing, Q, measured in cubic feet per second, will be the same at allsections in accordance with continuity of flow; so that 1 Q and A. Q

U1 '1) If the conduit is designed in accordance with the principles ofthis invention, the velocities must have the relation From theserelations, the proper cross-sectional area at any point can be founddepending upon the elevation of the point, to carry out this method. Forexample, if the area A, and the-velocity o, are fixed, the amount forany other area such as A may be computed from the above relations, thusIn order that the benefit of the method of this invention may be fullyrealized, sufficient space should be available to allow the necessaryvertical length of conduit to be secured. If it is desired to deceleratefully by this method, the flow from a given initial velocity 'v, to agiven final velocity 0,, the available height of conduit must be equalto the difference ofthe initial and final velocity heads, that isconstant from point to point along the lines of fiow, except for thesmall effect of surface friction. In other cases, however, particularlywhen limited height is available the method of deceleration by gravitymay be applied merely to the vertical or meridian component of theinitial velocity, leaving the whirl component to be converted bydiverting the flow away from the axis and reducing its amount by the useof the principle of constancy of moment of momentum, by which the whirlcomponents will vary inversely as the radial distance from the axis. Insuch an upwardly directed tube (Fig. 2) we thus have very efiicientmeans of converting both the meridian and whirl components of velocity,the meridian components being decelerated by the method of thisinvention and the whirl components by the use of a conduit spreadingaway from the axis and applying the principle of conserving the momentof momentum of the whirling flow.

In some installations it may be desirable to provide a smalladditionalheight to offset the tendency of the surface roughness of the conduitwalls to produce the efiect of divergence or enlargement; but if toomuch increase in length 1s allowed, the increase in extent of surfacewill more than offset any gain. On the other hand in many cases,particularly in small conduits where the surface resistance iscomparatively great, it may be advisable to reduce the height a smallamount below that corresponding to the difference in velocity heads, inorder to minimize the total loss. When the space limits do not permitsufficient vertical height for complete deceleration by gravity, induceddeceleration or diflusion may be added by giving the walls an additionaldivergence beyond that required by the gravity deceleration; but thisadditional divergence should not exceed about 4 or 5 if excessive lossesare to be avoided.

A conduit having less height than that corresponding to the reduction invelocity head will secure some advantage from the deceleration bygravity, but while the conditions will be better than in a similar tubeaving horizontal or downward flow, the full benefit of this principlewill not be secured if the height is materially less than the differencein velocity heads, since a distinct enlargement or diffusion loss willthen occur.

It is of course not desired to reduce the velocity completely to zerosince is necessary toleave a certain final velocity of discharge tocarry away the water, but this final velocity may readily be reduced toa small value by a slight increase in height when space is available forthis and for the required area of the discharge passages or tailrace.

In Fig.3 of the drawings a specific embodiment of the invention is shownillustrated in connection with a hydraulic turbine having a verticalshaft S and an upward discharging runner R. The inflow entering byintake 10 passes through the vanes of speed ring 11 and through guidevanes 12 to the runner R from which it discharges upward into the drafttube D formed as an annular expanding passage around the central core C.The core C provides an inner surface 14 formed as a surface ofrevolution of generally inverted conical form. The outer surface 15 ofthe draft tube is also formed as a concentric surface of revolutionspaced from the inner wall to provide successive outflow areas increasing in accordance with this invention to correspond to the gravitydeceleration of the discharge. The outer draft tube surface 15terminates in a circular ridge or crest 16 preferably above tail waterlevel 25 so that the discharge from the draft tube D into 'dischargepassage 17 passes above tail water level in the form of a siphon. Thissiphonic form of draft tube at its crest 16 may carry the outflow abovethe tailwater level and is particularly adapted to take full advantageof the principle of this invention since it thus permits the draft tubeto be of the exactly desired length without requiring an unnecessarylowering of the turbine runner or increased excavation. The use of thesiphonic arrangement is in effect equivalent to placing the entiredischarge stream in a partial vacuum.

In the turbine installation shown in Fig. 3, the draft tube D is of thespreading type, particularly adapted for a whirling discharge from therunner. The core C has a concrete base 20 with a central bore 20 and thehollow conical casting 21 is lowered through the bore of this base andsuspended from the annular shoulder 20' of the base as shown. The shaftbearing, 22 carried by the lower end of this casting 21 provides asupport near the runner R. which is built 'up of a hub 23 carrying theblades 24. in detachable sections so that the vertical opening abovewill not have to be large enough to pass the full diameter of therunner, but only the diameter of the hub 23.

The outer wall 15 of the draft tube D is formed by the surroundingportions 25 of the concrete subfoundation and by the liners carriedthereby. The whole arrangement is simple and compact providing acontinuous columnar support through stay vane rings 11 and 26 and theannular concrete body 25. The outflow passage 17 beyond the crest 16 islarge in area having a low velocityof flow.

The gradual. and continuous increase in area of the draft tube Dprovides for the deceleration of the outflow at substantially the samerate that gravity would decelerate recon-ea it it freely discharged. Thedeceleration may therefore be considered as due to the retarding efiectof gravity on each particle of the flow. By this deceleration thepressure is reduced below the corresponding static pressure and thepressure reduction varies directly as the depth at each point so thatthe pressure is substantially constant throughout the gravitydeceleration portion of the draft tube. l Vhen the runner is depressedto a'relatively low elevation the velocity head at its discharge is hi hin comparison with the net head on the tur ine. In the draft tube ofthis invention therefore substantially constant pressure is main-'tained in that ortion in which the velocity head is high in comparisonwith the net head llt is the object of this method of decelerating thevelocity to diminish the losses inherent in the ordinary, method, whichI have termed deceleration "by difi'usion, in which the deceleration isproduced (or induced) by the enlargement of area of the enclosing wallsalone, without the assistance of the direct action of gravity.

If a jet of water at a considerable velocity is dischargedhorizontallyinto a large body of water, the surface of the jet willexperience retarding forces from the surrounding water, and the outerportions of the jet will be retarded to lower velocities, resulting in aspreading of the jet in orderythat it may occupy the necessary area toaccommodate the given discharge at the reduced velocity. By this actionthe entire stream is gradually spread out or diffused and its velocityis finally reduced to zero, its original velocity head being dissipated.For instance where a tube discharges into a body of water the jet fromthe tube can be vividly seen to spread and decelerate the drag of thewater on the jet, causing the water to circulate in closed paths aroundthe path of the jet. By encloslng the jet in a gradually enlargingconical passage having a small angle of divergence of its walls, thedissipation of energy will be reduced and thedeceleration will beaccomlished without the loss of the whole of the initial velocity head.But whether a jet is surrounded by a large body of water or by anenclosing casing only slightly'larger than the free jet, any enlargmg ofcross-section of the stream, and consequently any deceleration, must beinitiated by, and accompanied by, resistances acting on the surface ofthe jet, and consequent losses. Without such action the jet wouldcontinue unchanged in area and velocity and there would, be no velocityhead conversion.

The diffusion loss canbe made evident by reversing the flow through ahorizontal conical pipe. When the flow is in the direction involvingcontraction of area the loss of head will be merely that due tohydraulic ing'to the velocity head, the conversion of which is desired.

The method of this invention is applicable to all points in hydraulicturbines, umps, ejectors or other hydraulic insta lations where it isdesired to convert kinetic into potential energy of the flowing fluid.

In Fig. 4 the invention is illustrated in connection with a verticalshaft pump having impeller 30 on shaft 31. The flowen- I tering fromintake 32 below passes upward through the runner and into thedecelerating passage 33 formed to convert the kinetic energy of the flowinto gravity head in accordance with the principle of this invention.This decelerator 33 thus takes the place of a difiuser in the pumpdischarge and attains a much more eflicieht conversion of the kineticenergy of the discharge with a resulting increased eificiency for thepump as a whole.

In Fig. 5 a horizontal shaft pump is shown in vertical elevation withthe runner on shaft 41 discharging into a volute casing 42 in which theoutflow is collected and directed vertically upward into the conicaldecelerator 43 formed in accordance with this invntion' to give alowering of the flow velocity corresponding to the vertical elevationsat successive points.

In Fig. 6 the axis of the discharge decelerator 43 is shown as inclinedbetween the vertical and horizontal positions. In this inclineddecelerator successive sections are formed to correspond to thedeceleration of the flow at the meanrelevations of the respectivesections.

In Figs. 7 and 8 a horizontal shaft turbine is shown having a runner 50with substantially axial discharge into a draft tube "1). This drafttube D is of the spreading type turning the flow and expanding it toconvert the energy of the whirl velocity :into pressure head anddelivering it to the expanding spiral collector passage 51 openingupward into the decelerator passage 52 formed in accordance with thisinvention to expand accordingly as the velocity of the outfiowis loweredan amount corresponding to the action of gravity.

Instead of decelerating the velocity of a fluid stream by enlargement ofthe crosssectional area of the enclosing conduit walls without'regard tothe general direction of flow as it afi'ects the elevation of successivesections, this invention so relates the velocity head and the elevationhead of successive sections'that the velocity head will be convertedinto elevation head, or gravity rounding conduit walls that thedeceleration will take place at substantially constant pressure, thevelocity head being reduced at a rate definitely corresponding to theincrease in elevation of successive sections of the stream. By enclosingthe stream by walls proportioned in accordance with the reductloninvelocity head corresponding to this principle, a conduit is provided inwhich the deceleration may be considered to be produced by gravityrather than by diffusion. As applied to hydraulic turbines thisprinciple secures the reconversion of velocity head of the waterdischarged from the runner into .efiective elevation head in a manner somuch more efficient than any heretofore applied that notableimprovements may be effected in the design and performance of turbinesparticularly increases in their efiiciencies and a'notable extension inthe range of available specific speeds.

It is estimated that decelerators capable of converting velocity headinto efiective head with a loss of less than ten percent of the velocityhead can be constructed by the use of these principles, and the rincipleof this invention will be applicab e with advantage in many situationswhere the deceleration was heretofore usually accomplished in downwarddirected passages. I claim g l. A tube for transforming kinetic energyof flow into potential energy, the cross sectional areas of said tube atsuccessive vertical points being regularly enlarged, in accordance withthe vertical elevation of said points above any given datum, so that thevelocity is so related to the elevation at each section that the sum ofthe velocity head and elevation above said datum will remainsubstantially constant.

2. A hydraulic conduit having areas so proportioned that for a definitequantity of fluid flowing the velocity computed by dividing the quantityby the area is so related to the elevation of the section that the sumof the velocity head and elevation above any arbitrary datum will remainsubstantially constant for each section.

3. A hydraulic conduit for transforming kinetic energy of flow intopotential energy arranged so that the difference in elevationbetween'its inlet and discharge ends is equal to or greater than thediflerence in the velocity heads of the entering and discharging water.

4. A hydraulic conduit fortransforming kinetic energy of flow intopotential energy arranged'so that thediflerence in elevation between itsinlet and discharge ends is equal to or greater than the diflerence inthe veloc ity heads of the entering and discharging water, and havinginlet and discharge areas proportioned in accordance with said velocityheads. I

5. A hydraulic conduitfor transforming kinetic energy of'flow intopotential energy arranged so that the difference in elevation betweenits inlet and discharge ends is equal to or greater than the differencein the velocity heads of the entering and discharging water, saidvelocity heads being computed in accordance with said inlet and outletsections.

6. In a hydraulic machine or apparatus, means for decelerating thevelocity of flow comprising an upwardly directed conduit havingsuccessive areas proportioned to maintain the sum of the velocity headand elevation substantially constant.

7 A hydraulic conduit for transforming kinetic energy of flow intopotential energy arranged sothat the difference in elevation between itsinlet and discharge ends is. equal to or greater than the difference inthe veloc ity heads of the entering and discharging water, said velocityheads being computed to include the velocity components in planescontaining the axis of the conduit.

8. In a hydraulic machine or apparatus, means -for decelerating thevelocity of flow comprising an expanding conduit having a substantiallyconstant pressure throughout.

9. In a hydraulic machine or apparatus, means for decelerating thevelocity of flow comprising an expanding conduit in which thedifl'erence in pressure at one end and the other is substantially lessthan the pressure head corresponding to the height of the conduit fromone end to the other.

10. In a hydraulic machine or apparatus, means for decelerating thevelocity of flow comprising an expanding conduit in which the variationin pressure is substantially less than the pressure head correspondingto the height of the conduit, ad a discharge pas sage from said conduitdissharging below the water surface and having an area such that thevelocity head is low compared with the velocity head in said conduit.

11. In a hydraulic machine or apparatus, means for decelerating thevelocity of flow comprising an expanding conduit having substantiallyconstant pressure throughout and of suflicient height to decelerate themajor portion of the velocity.

weenie 12. In a hydraulic turbine, a draft tube g in which theelevations of successive sections increase to maintain substantiallyconstant pressure throughout the portion: in

which the'velocity heads are high in comadapted to decelerate thevelocity of outflow from a turbine runner with only such energylosses,as are due to pipe friction.

14:. In a hydraulic machine or apparatus, means for deceleratingthevelocity of flow comprising a conduit ada ted to decelerate the meridiancomponent 0 velocity at a rate corresponding to the rate of decelerationby gravity. 7 p

15. lln a hydraulic machine or apparatus, means for decelerating thevelocity of flow comprising a conduit adapted'to decelerate the meridiancomponent of velocity at a rate corresponding to the rate ofdeceleration by gravity, and having a spreading flow outward away fromthe axis of the conduit to decelerate the velocity of whirl.

16. A conduit constructed and arranged to convert velocity head intoelevation head without substantialchange in intensity 01' pressure atsuccessive points'in the conduit.

17. An. upwardly directed conduit continuously enlarging incros's'sectional area at a rate corresponding to the deceleration due togravity and so formed that the loss of head for a given quantity offluid flowing per second is independent of the direction 01' flow. I

18. The method of converting kinetic energy of flow into potentialenergy comprising directing the flow upwards and enclosing it withinwalls forming a conduit, the cross-sectional area of which enlargesi-nthe direction of flow an amount suflicient to reduce the velocity fromone point to another in such proportion that the velocity headdiminishes by the same amount that the elevation increases.

19. The method of converting kinetic energy of flow into potentialenergy comprising directing the flow upward and guiding it between wallson expanding lines such that the pressure is maintained'substantiallythe same.

20. The method of converting kinetic energy of flow into potentialenergy comprising directing the flow upward and guiding it between wallson expanding lines such that the pressure at the lower portion of thestream is substantially the same as that at the upper portion-of thestream.

21. The method of converting kinetic energy of flow into potentialenergy comprising directing the flow upward and guiding 1t between wallson expanding lines such that the sum of the velocity head and elevationis substantially constant.

22. The method ofconverting kinetic energy of flow into potential energycomprising directing the flow upward and guidin it between walls onexpanding lines sac that the sum of the velocity head and elevation issubstantially the same at the upper portion of the stream as at thelower.

23. A hydraulic conduit for transforming kinetic energy of flow intopotential 'ener'gy, in which the decrease in velocity head from onesection to another is not greater than the increase in elevation of thesecond section above the first.

24. A hydraulic conduit for transforming kinetic energy of flow -intopotential energy in which the decrease in velocity head from theentrance to the discharge section is not greater than the increase inelevation of the discharge section over the entrance section. r

25. A hydraulic conduit for transform-' pending conduit arranged tocarry the flow through an increase in elevation, the crosssectionalareas at the entrance and discharge ends of said decelerator being soproper-- tioned that said increase in elevation is equal to a majorportion of the difierence in velocity heads at said entrance anddischarge sections.

EwIs FERRY MOODY.

